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There is no denial that renewable energy is considered to be the most cost-competitive source of clean power in many parts of the world. Saudi Arabia's vision 2030 aims at achieving the best by using different sources of renewable energy such as solar energy, wind energy, and others. The use of solar energy in particular for power generation will decrease the dependency on oil, and thus, decrease the greenhouse gasses. Solar panels efficiency tends to decrease with the accumulation of dust on their surface. Thus, a cleaning process requires assigning and employing labor, which increases the cost of running as well as high cost of machinery. The current study focuses on assessing and designing a simple auto self-cleaning system in order to improve the efficiency of the solar panel. The results showed that for the Al-Khobar region, Eastern Province, Kingdom of Saudi Arabia, the efficiency of the solar panels after cleaning was increased from 6% to an average of 12% at nominal temperature of 27 °C. In addition, the average power output was increased by 35% during the day time. In addition, the normal efficiency of the solar panels before cooling was between 10% to 15% at 42 °C. After cooling, the temperature of solar cells decreased to 20 °C and the efficiency increased by 7%. Moreover, the output power was increased by 31% with maximum efficiency of 32% at noon time. [ABSTRACT FROM AUTHOR]

This study aims to investigate the feasibility of using raw biogas as the main fuel in homogeneous charge compression ignition (HCCI) engines and to identify the effects of different trace elements found in biogas on engine performance and emissions. This study was conducted using many models that simulate the operation of HCCI process. These models include the chemical kinetics, combustion model, and the heat transfer models. Raw biogas composition was selected based on the most available traces. The traces that were studied are Hydrogen Sulfide (H 2 S), Ammonia (NH 3), Carbon monoxide (CO), Nitrogen (N 2), Oxygen (O 2), and Water vapor (H 2 O). Other parameters like the equivalence ratio, intake temperature, and pressure were also studied. It was found that raw biogas mixtures could produce higher power outputs in the presence of H 2 S and NH 3. However, H 2 S and NH 3 were found to increase the SO x and NO x percentages owing to their higher in-cylinder temperatures. Other traces such as CO and H 2 O can reduce the power output, but at the same time, they can reduce the engine NO x emissions but not the CO emissions. Engine performance was positively affected by increasing the intake pressure and equivalence ratio within the studied ranges. However, higher intake temperatures and reduce the engine efficiency and increase the engine emissions. On the other hand increasing the compression ratio (CR) increase the system efficiency but up to a certain limit. Considering the exhaust gas residual (EGR), this parameter reduce system performance but at the same time lower the NO x emissions significantly. A sensitivity analysis for the mentioned parameters indicates that EGR is the most effective parameter while CR are the least significant one. • The potential of using raw biogas in HCCI engines was examined. • The effect of different biogas traces on engine performance and emissions was studied. • Raw biogas can enhance the engine efficiency and power output. • The presence of H 2 S and NH 3 increases NO x and SO x emissions. • Sensitivity analysis indicated that EGR has the most significant effect on system performance. [ABSTRACT FROM AUTHOR]